Category

Published on

20 Mar 2007

Abstract

The ability to manipulate and identify the properties of single biological molecules with the potential of characterizing biological processes at the most fundamental levels can significantly facilitate rapid diagnostics and therapeutics. Fabrication of solid-state devices investigating bacteria, viruses, proteins and even at such smaller sizes as of DNA can create a large arsenal of highly specific and ultra-sensitive biosensors and systems. From a long list of nano-scale solid- state biological sensors pursued in our lab, two important silicon based electrical frameworks will be discussed. These novel systems have been used to characterize DNA molecules. First, a method employing metal nano-electrodes with nanometer scale spacing will be presented. These nano-electrodes were used to measure the effects of the GC-content of the DNA on its DC conductivity. A dramatic decrease in conductance was seen on heating the DNA devices, analogous to an electrical fuse, attributable to complete or partial denaturing of the ds-DNA molecules that bridged the nanogaps. These findings have applications in non-optical detection of extremely low concentrations, biophysical studies of charge transport, and control of DNA-modified materials. Second, solid-state nanopores, progenitors of rapid and cheap next-generation DNA sequencing “machines”, selective to important DNA sequences will be described. To date, this work is the first evidence of engineering selectivity in solid-state nanopores. Distinctly different translocation signatures and event frequencies were discovered for important DNA targets.

Artist's rendition of nanopore channels Image courtesy of Seyet LLC

The selective solid-state nanopores realized in an array format can open avenues to novel devices for sequencing, detection of single nucleotide polymorphism, expression analysis, etc. as well as detection of specific proteins using specific ligand-receptor systems from very few copies of the analytes. Such selectivity can be electrically measured and can be used for direct label-free sequencing and detection of nucleic acids. These devices can potentially mimic the exquisite selectivity found in natural biological channels in cell or nuclear membranes, and help unravel the physics of selective and facilitated transport of bio-molecules in nanoscale channels.

Bio

Dr. Samir Iqbal is working in the Laboratory of Integrated Bio-Nano Applications (LIBNA) in Birck Nanotechnology Center. He received his undergraduate degree in Electrical Engineering from NED University of Engineering and Technology, Karachi, Pakistan. He joined the School of Electrical and Computer Engineering at Purdue University in direct Ph.D. program in 2002. In graduate school, he received a number of awards and distinctions, most notably the Magoon Award for Excellence in Teaching from the College of Engineering and an NSF fellowship to attend summer school at Northwestern University, Illinois, USA. He received his doctoral degree under the supervision of Professor Rashid Bashir in February 2007.